A Faraday sensor is configured to intercept a quantity of ions incident on the Faraday sensor. As the ions strike the Faraday sensor, an electrical circuit connected to the Faraday sensor senses a current representative of the quantity of ions or the ion beam current. In one instance, the ions may be positive ions and the electrical circuit may include a current meter coupled to ground. As the positive ions strike the Faraday sensor, electrons are drawn from ground through the current meter to combine with the positive ions. The current meter measures the electron flow which is representative of the ion beam current. One type of Faraday sensor may have a cross sectional cup shape and may be referred to as a Faraday cup.
The Faraday sensor, the electrical circuit connected to the Faraday sensor, and the connections there between and elsewhere in the electrical circuit may suffer from a variety of fault conditions that can lead to inaccurate ion beam current measurements. Such fault conditions may include wiring faults or Faraday sensor faults. Wiring faults may include unsatisfactory connections or damaged conductors such as crushed or burned conductors. Faraday sensor faults may occur from conductive particle buildup on insulators of the Faraday sensor. In one instance, the particle buildup may be graphite buildup caused by ions striking a graphite Faraday sensor. Such fault conditions may manifest themselves as short circuits to ground, resistance to ground, capacitance to ground, and/or other circuit anomalies.
Inaccurate ion beam current measurements from the Faraday sensor system can lead to degradation in the performance of a system utilizing the Faraday sensor system. For example, Faraday sensors are commonly utilized in ion implanters. An ion implanter generates a quantity of ions and directs the ions to a wafer for implantation. The Faraday sensor system may be utilized to sense a quantity of ions for implantation and provide an electrical signal representative of the quantity of ions to an associated controller such as a dose controller. The dose controller may receive and monitor the electrical signal from the Faraday sensor system to monitor and control the implant so that the wafer is implanted with the proper dose. An inaccurate ion beam current reading from the Faraday sensor system can lead to inaccurate dose control by the dose controller thereby creating an undesirable over-dose or under-dose implantation into the wafer. Accordingly, it would be desirable to test the Faraday sensor system.
One conventional method of testing the Faraday sensor includes a technician manually coupling a high voltage across the Faraday sensor to monitor the continuity of the Faraday sensor. Drawbacks with this conventional approach include the human involvement necessary to test the Faraday sensor. Such human involvement requires expertise that may not be readily available and is subject to human error in making an assessment of the condition of the Faraday sensor. Such conventional manual tests may also not be made as often as desired given the human involvement required.
Accordingly, there is a need in the art for an automated Faraday sensor test system.